Since its release in 2003, IEC 61850, a standard that defines communications protocols for intelligent electronic devices associated with power systems, has been rapidly adopted by utilities around the world. Nearly 100 percent of European utilities use this standard, but very few do so in North America. Here in the U.S., lack of adoption generally centers on the perceived risks of moving to IEC 61850 and a limited view of the technology’s benefits.

That’s short-sighted because 61850 delivers a comprehensive toolkit of best practices for substation automation and other application domains. It’s the only non-proprietary international standard that specifically addresses substation control at protection speeds, making it a great choice for utilities working hard to modernize their transmission and distribution systems. It also makes it easier to move data from the grid edge, where many sensors and other devices reside.

This article covers why utility engineers in North America might want to give this standard another look.

A Way of Life

IEC 61850 was designed by leading substation automation experts throughout the world to simplify the process of automation. It is much more than a communication

protocol; it is a way of life, a standard that goes beyond describing how data is transferred and received. It defines

how data is executed and stored, and it covers device specifications, such as surge withstand, temperature, electromagnetic interference (EMI) and other factors.

Back in 1996, when the IEC Technical Committee 57 began work on an automation standard to replace the IEC 60870-5 set of standards, the group had the following high-level goals:

• Expand the protocol standard to become a comprehensive automation standard
• Use existing standards where possible, specifically Ethernet and MMS
• Establish a well-designed object definition methodology
• Incorporate a machine-readable configuration language for all aspects of the automation
• Facilitate high-speed peer-to-peer communication for distributed control system that was not a master-slave approach
• Integrate conformance testing requirements

The resulting IEC standard released in 2003 accomplished all of the goals. Specifically, 61850 includes the following major features:

• Support for project management (signal names, top-down design, testing aspects)
• A machine-readable configuration language (XML)
• Simplified representations of physical apparatuses and their operations
• Mappings to protocols (ISO 8606 MMS and 802.3 Ethernet)
• A publish-subscribe mechanism for peer-to-peer communication (GOOSE)
• A method to digitize data close to the source (Sampled Values)
• Conformance testing methodologies

Given these features, 61850 allows for high-level design with sufficient detail for use as a procurement document, plus it lets engineers prepare a final configuration containing the as-built model of the complete system. This final configuration file can be used to automatically generate documentation and for it to be input into simulation and test devices.

IEC 61850 attempts to create a “step-by-step cookbook” for the construction of automation systems. Cookbooks contain ingredients as well as well-defined parameters, such as standard measurements – a cup, a teaspoon, etc. – and well-defined activities, such as creaming butter or baking at 375 degrees. If you didn’t have such details, you couldn’t bake a uniform cake repeatedly. That’s one of the main advantages IEC 61850 offers. Like a cookbook, it is a comprehensive resource of well-defined automation parameters, activities and terminologies.

In addition to its flexibility, consistency and breadth, IEC 61850 specifies a well-defined and machine-readable configuration language that can be used during all stages of the automation system design. It facilitates definition of the physical equipment, such as breakers, busbars and instrument transformers, lists supported services and objects and outlines the final as-built functional and communication systems including signal flows.

Advantages of IEC 61850 Over Legacy Protocols

The traditional workflow for power automation systems inhibits innovation. That’s because the traditional approach used in the U.S. aims to minimize differences between the previous automation system and the current iteration. In contrast, the IEC 61850 approach accommodates the needs of the larger system, including enterprise-level systems, and it also focuses on functionality.

IEC 61850 accomplishes this by decomposing the requirements of the larger system and codifying a design philosophy, which simplifies engineering efforts. Legacy protocols such as Modbus and DNP3 mostly focus on the data transfer portion of the automation system. IEC 61850 expands beyond the data, which lets the user design automation systems based on what should be done as opposed to how the data should be transferred.

In addition, the standard establishes a consistent naming convention for signals and data objects. The standard spans from the central system database to individual signals and objects within each device. Because of this consistency, it is much easier for systems at various levels to aggregate information from individual devices. For example, the IEC 61850 name for Phase A-to-B Volts is identical for any 61850 device with that piece of data.

As another example, aggregating total power consumption is simply a matter of adding the 61850 values of “TotW.” Typically, what happens now is that data coming out of a device must run through multiple translators associated with various devices before it gets to the enterprise system that actually deals with the data. Just as communication changes when a group of children plays “whisper down the alley,” this oft-translated data may lose some detail by the time it reaches the enterprise system. This is because almost every protocol is slightly different. Pieces of information in the source protocol may have no representation in the destination protocol. When that happens, the data gets dropped, and some data detail may be lost in translation. IEC 61850’s consistency eliminates the translation steps.

Support for a variety of methods to transfer data values is yet another advantage of this standard. It facilitates traditional polling by object (the "pull" model) as well as spontaneously generated data (the “push” model). The push model is further divided into data that is published only if interesting, such as alerts or exception reports, and data that is published on a periodic schedule. The push model can dramatically reduce the communications bandwidth compared to the pull models of traditional protocols.

IEC 61850 communications can be of two types: point-to-point as well as point-to-multipoint. The first type is used for the flow of data between two pre-defined devices. Point-to-multipoint communication comes into play when a single piece of information needs to be conveyed simultaneously to multiple recipients, typically at very high speeds.

The standard was designed for extensibility in that future capabilities are fully backwards compatible with previous equipment versions. This feature is important to protect prior investments in automation. For example, older 61850 products can accommodate protection functions that were defined after the release of the older product. Such extensibility also allows vendors to offer capabilities beyond what is written in the standard as product differentiators.

A final major advantage of 61850 is the ability to define the “wireless substation” where information is digitized at the source and placed upon the main communication network for all devices to use. IEC 61850 uses Generic Object-Oriented System Event (GOOSE) messaging, which is designed to be vendor independent, as well as sampled values (SV) to transport the analog voltage and current information throughout the system. This allows most pieces of equipment to use only a single power connection and an Ethernet port without the tangle of device-to-device wiring. It eliminates the manual, error-prone wiring work and documentation required in legacy approaches require.

Why “No” Should Be “Yes”

The IEC 61850 concept has been criticized in many ways. The first criticism is that the standard is very large and difficult to learn. That’s true. The first edition of 61850 contained 14 parts with about 1,500 pages. The 2009 version contains over 40 parts with many more pages. Still, this volume of information is a necessity to describe enough detail to accomplish the cookbook approach.

IEC 61850 has also been criticized for using cryptic names instead of point numbers.

The naming rules for 61850 use well-defined, but short abbreviations to name data objects. For example, “MMXU1.PPV.phsAB.cVal.mag.f” is the name of the deadbanded voltage primary magnitude on a 3-wire delta power system from phase A-to-B. While not exactly human-readable at first glance, each of the components is well-defined. In contrast, legacy protocols such as DNP3 might indicate the same information as “Analog-Input point number 352,” and engineers would be sent scrambling to consult the individual product documentation to determine where the corresponding data scaling factors are located.

Likewise, the IEC 61850 configuration language is very complex and difficult to read. But, the language is meant for information exchanges between computer applications and isn’t meant to be changed by humans. Tools exist that can convert this language into human-readable form.

Another perceived disadvantage of 61850 is the rapid pace of the standard’s evolution. This is the same set of “growing pains” that all standards experience. However, it is a particular concern to automation systems that are expected to be in service for a longer time span than a single version of the standard. The only solution, which has also been adopted, is to strive for both forwards and backwards compatibility.

Some users balk at the rigidity of the 61850 approach to substation design and believe that there are parts of 61850 that do not need to be followed. On the contrary: The full benefits of 61850 are only realized when adherence to the standard is followed throughout the design. For example, users may wish to bypass the portion of the configuration that assigns the network addressing within the System Configuration Description (SCD) file because this was not needed in legacy systems. However, this seemingly small change to the 61850 cookbook results in a system where verification of device address assignment is impossible, leading to possible failures in the operational system. It also complicates diagnosis of problems during maintenance. Furthermore, an estimation of traffic volumes using the SCD file becomes impossible.

Ultimately, the design rules of 61850 reduce the effort of generating valid automation configurations. 61850 eliminates the need for error-prone manual spreadsheets to transfer information between systems. It defines a method to communicate from the end device all the way to the central database without modification. While the standard has a steep learning curve, it eliminates work, complexity and the risk of manually introduced data errors in the end. The key to managing complexity is to use appropriate tools that can hide the complexity.

The standard also cuts the risk of construction errors because, if fully implemented, all point-to-point wiring can be eliminated. Since wiring faults in automation systems contribute a significant number of failures, the reliability of the system increases dramatically. What’s more, both SV and GOOSE inherently contain “heartbeat” signals that allow the automation system to self-monitor for faults and place themselves into safe mode when equipment failures occur.

Clearly, there are plenty of benefits in 61850 to counteract perceived disadvantages. That’s why it is time for U.S. engineers to give this standard a second look and, better yet, a try.

For users new to 61850, the migration might look very difficult, but there are ways to mitigate the risks. Two approaches have been successfully used by US utilities: “baby steps” and a full 61850.

The baby-steps approach is essentially cherry-picking the easy-to-use features and extending an existing automation system. For example, a GOOSE scheme can be employed to provide interlocking of control decisions and the controls can be implemented in 61850 as point-to-point requests. This has the advantage that only very small parts of 61850 need to be understood to successfully implement. The disadvantage of this approach is that it is very easy to take shortcuts to the standard 61850 configuration system that will result in a later possible re-design.

The full-61850 approach involves a deep dive into the 61850 standard to build a completely new automation system for a new application. This requires a major commitment by the user and a full understanding that the first (and second and maybe third) implementation of 61850 will be more expensive than the corresponding legacy system. This technique, however, has the advantage of avoiding false starts and revealing the full power of 61850 in the first implementation.

The cost savings of the wireless substation, along with the wider range of protection and control applications utilities can implement with 61850, raise this standard beyond conventional legacy techniques. 61850 delivers true interoperability and supports seamless device integrations. It may take some study up-front, but it will save utility engineers time and trouble on the back-end.

What are you waiting for? Isn’t it time you looked at 61850 for your substation automation projects?